Device for detecting the presence of objects in a blind angle of a motor vehicle

ABSTRACT

A device for detecting the presence of objects in a vehicle&#39;s blind spot. The invention relates to a device for detecting the presence of objects in a vehicle&#39;s blind spot, where the objects contain at least one ferromagnetic material whereby they distort the earth&#39;s magnetic field. The device is mounted on a vehicle that has at least one blind spot. The detection device can detect the object located in the blind spot because it is provided with a unit for detecting the distortion of the earth&#39;s magnetic field caused by the object. Preferably it includes a logical circuit with neural nets for processing the signals received from the sensors.

AIM OF THE INVENTION

The invention relates to a device for detecting the presence of objectsin a vehicle's blind spot, where the objects contain or are manufacturedfrom a ferromagnetic material whereby they distort the earth's magneticfield. The device is mounted on a vehicle, that has at least one blindspot, in such a way that the detection device can detect the objectlocated in the blind spot.

STATE OF THE ART

Conventional vehicles are usually provided with rear view mirrors,consisting generally of one internal mirror and two external ones, whichenable the user or driver to look behind without having to turn himselfaround. However, in spite of being provided with a series of mirrors,there are usually some areas, called blind spots, that are not coveredby said mirrors.

Various alternatives exist, such as the use of radar devices, the use ofpivoting rear view mirrors, etc., which are intended to cover theseblind spots and the danger they present. However, they have not solvedthe problem completely and/or they are expensive devices and, therefore,their market introduction is limited.

It is also known to use systems that capture an image directed towards ablind spot using a CCD camera and show said image to the user by meansof a screen placed inside the vehicle. These systems enable the user tosee the blind spots without having to sit up, however, they have aseries of disadvantages: they require image transmission systems of asufficient standard so that the user can perceive a clear image, whichmeans working with a large number of pixels, there must be spaceavailable inside the vehicle to position the corresponding screen, thesystem does not process the image, it only transmits it, etc. Therefore,these systems are expensive and do not actively contribute to detectingrisk situations.

Also there are some devices for detecting the presence of objects, ofthe type that are mounted on a vehicle, that has at least one blindspot, with the detection device being able to detect an object locatedin the blind spot and comprising: a receiver capable of detectingelectromagnetic waves, with a focusing device, and a photosensor thatconverts said received electromagnetic waves into electric signals, anelectronic circuit that converts the electrical signals into digitalisedsignals, a logical circuit that analyses the digitalised signals inorder to analyse the presence of objects in the blind spot that moverelative to said vehicle, and which emits output signals that varyaccording to the analysis result, and indicator elements, activated bythe output signals that can be perceived by the driver. These deviceshave been described in document ES P200000378, which is herebyincorporated herein by reference, and they represent a series ofimprovements made to the devices existing previously on the market.

However, optical type systems are not problem free in certain lowvisibility situations (glaring sunlight, fog, etc).

SUMMARY OF THE INVENTION

The aim of the invention is to overcome these drawbacks. This aim isachieved by means of a device for detecting the presence of objects ofthe type indicated at the beginning, characterised in that it isprovided with means for detecting said distortion of the earth'smagnetic field caused by said object.

In fact, detection of the earth's magnetic field as well as the possibledistortion thereof is not influenced by environment conditions (sunlightglare, fog, etc.) which cause problems in the optical type detectiondevices. In addition, the invention enables competitively priceddetection devices to be developed.

Preferably, the detection device comprises: [a] at least one magneticfield sensor, suitable for producing electrical signals according to themagnetic field detected, [b] an electronic circuit that converts theelectrical signals into digitalised signals, [c] a logical circuit thatanalyses the digitalised signals in order to analyse the presence of theobject in the blind spot, and which produces output signals that varyaccording to the analysis result, and [d] indicator elements, activatedby the output signals.

The earth's magnetic field is distorted by the presence of aferromagnetic material. In this way, a conventional vehicle comprising alarge number of components made from ferromagnetic materials, distortsthe earth's magnetic field surrounding it. The presence of an object,also made at least partially from ferromagnetic materials, causes themagnetic field to be distorted a second time. This distorted magneticfield, once captured by the sensor and processed by an electroniccircuit, is analysed by a logical circuit which determines whether thedetected values correspond to the presence of an object in the blindspot.

The sensors can be of any kind providing that they fulfil therequirements of the invention. In this sense, they can be, for example,flux gate magnetometers (flux-gate sensors), Hall type sensors,magnetoinductive sensors or mangnetoresistive sensors. The resolutionlevel which they must preferably be able to detect must be less than orequivalent to 0.01 Gauss.

The detector must be able to locate the object in the space around thevehicle, and in particular, it must be able to know whether it is in theblind spot. In this sense, it is advantageous that the sensors are ableto detect at least two of the three spatial components in a magneticfield.

The detected magnetic field signals can be influenced by the inclinationangle of the vehicle with respect to the horizontal. Therefore, it isadvantageous that the detection device according to the inventioncomprises, in addition, a device for measuring the inclination angle ofsaid vehicle with respect to a horizontal plane. In this way, saidinclination angle can be taken into consideration when assessing thedetected values. This inclination angle measuring device can be, forexample, a device that detects the third spatial component in themagnetic field, an inclinometer, etc.

The sensors, in particular the flux-gate sensors, can be current orvoltage fed. However, since the sensitivity of the sensor depends on thecurrent amplitude circulating through the primary circuit, it isadvantageous that the sensors are of the current fed type.

Preferably, the detection device reads said magnetic field at least onceevery 100 ms.

Advantageously, the detection device can distinguish whether the objectis another approaching vehicle or whether it is another object. In thisway, the detection device can eliminate possible false alarm situationswhen it detects the presence of objects that do not represent any dangerfor the vehicle, such as vehicles travelling in the opposite direction,static objects on the roadside, parked vehicles, etc. The logicalcircuit preferably comprises neural nets. The detection device cantherefore undergo a training process which enables it to ascertain thepotential risk conditions for the vehicle from the other conditionswhich, although they distort the earth's magnetic field, do not pose anypotential danger as far as the vehicle is concerned.

The detection device has preferably an action radius of at least 4meters , measured from each of said sensors. This action radius cantherefore cover substantially the blind spot in most conventionalvehicles.

It is advisable that the sensor is as far away as possible from theferromagnetic materials in the vehicle, since these also distort theearth's magnetic field. In this sense, it is convenient that the sensoris placed within an outside rear view mirror assembly on said vehicle.

On the other hand, the distortion of the earth's magnetic field that iscaused by a vehicle is relatively small. In this sense, it can beadvantageous to position the sensor in the rear of the vehicle. In thisway, the action radius can be extended towards the rear of the vehicle.

As already indicated, the vehicle itself distorts the earth's magneticfield. In order to remove this distortion from the signal detected bythe sensors, it is advantageous to have two sensors placed insymmetrical arrangement with respect to the vehicle's longitudinal axis,and to calculate the difference between the signals produced by each ofsaid sensors. In addition, with calibration data (which are provided bythe sensor values when the vehicle is in motion, when no objects arepresent), it is possible to subtract from the signal produced by each ofsaid sensors, the part corresponding to the distortion of the earth'smagnetic field caused by the vehicle itself. Preferably, the detectiondevice has a sensor in each of the outside rear view mirrors on saidvehicle.

Optionally, it is possible to improve the detection device's ability toanalyse risk situations, by adding to the detected characteristics of anapproaching object, the ability to detect whether the vehicle carryingthe detection device has begun to indicate that an object isapproaching. In particular, it is advantageous that the detection deviceis able to detect when the indicator light is illuminated and/or candetect when the vehicle steering wheel is turned.

It is also recommendable that the detection device is able tocommunicate various signals to the vehicle user or driver, which enablethe warning signal to be adjusted according to the risk of collision.Therefore, it is preferable that the indicator elements include lightsignals with at least two colours, each colour indicating a differentlevel of warning. It is also advantageous to include an output elementwhich provides a pictogram representation, said output element being aLED matrix or a graphics screen.

Moreover, a risk situation may arise if a passenger in the vehiclecarrying the detection device opens a door without looking if anothervehicle is approaching from behind. It is, therefore, advantageous thatthe detection device also indicates said risk situations to the vehiclepassengers.

Finally, it is advantageous that the detection device can act upon thedoor closing action. Therefore, for example, it can lock a door if arisk situation is detected

As indicated above, the distortion of the earth's magnetic field is on asmall scale. In this sense, it is useful for detecting objects in theblind spot. However, other object detection devices exist, such as forexample that described in the afore-mentioned document ES P200000378,which detect objects at greater distances, including outside thevehicle's blind spot. It can be advisable that the detection devicecomprises, therefore, other means for detecting the presence of objects,as well as the means for detecting said distortion of the earth'smagnetic field. In this way, it is possible to combine the advantagesgained from the detection of these magnetic distortions (such as forexample their insensitivity to climatological conditions, glaringsunlight, etc.), with the advantages gained from other detection means(such as for example the greater action radius).

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages and characteristics of the invention can be appreciatedfrom the following, non-limiting description, of a preferred embodimentof the invention, with reference to the accompanying drawings, in which:

FIG. 1 is a graph showing the magnetic field detected during anover-taking manoeuvre.

FIG. 2 is a graph showing the magnetic field detected during a turn.

FIG. 3 is a graph showing some functions of the magnetic field during aturn.

DETAILED DESCRIPTION OF THE INVENTION—EXAMPLES OF EMBODIMENTS

There follows a description of the embodiment of the invention. To thisend, the description starts with a vehicle provided with two 2-waysensors each housed in a rear view mirror on the vehicle. In theinterest of simplicity, it has been assumed that the co-ordinate originis the geometrical centre of the vehicle and that the X axis is thevehicle's longitudinal axis. The Y axis is horizontal and the Z axis isvertical. Each sensor (r1 and r2) detects the two components Bx and Byin the magnetic field. The vehicle is orientated so that its X axis isparallel to the NS axis in the earth's magnetic field, and the vehicleis facing magnetic north.

FIG. 1 shows the magnetic field (Bx and By, in Gauss) that is detectedwhen the vehicle is overtaken by an object (another vehicle) in functionof the distance (in cm) between the centres of the two vehicles. Thecurves 1 and 3 correspond to the sensor in the rear view mirror on thedriver's side (r1), while the curves 2 and 4 correspond to the sensor inthe rear view mirror on the passenger's side (r2). These curves are afunction of the vehicle's orientation in relation to the earth'smagnetic field.

FIG. 2 shows the magnetic field (Bx and By, in Gauss) that is detectedwhen both vehicles turn (for example if both vehicles travel along acurve maintaining the relative position between them constant) infunction of the angle turned (in sexagesimal degrees). The curves 5 and7 correspond to sensor r1 whereas the curves 6 and 8 correspond tosensor r2. The curves 9, 10, 11 and 12 are the curves corresponding to aturn made by the vehicle carrying the detection device when no object ispresent (when no second vehicle is present).

One way of performing calibration is by means of the following method:

1. Turn the vehicle 360° and determine the values (Bxmax, Bxmin, Bymax,Bymin) for each of the sensors r1 and r2

2. Calculate the correction and offset factors:Xcorr=(Bymax−Bymin)/(Bxmax−Bxmin)Ycorr=(Bymax−Bymin)/(Bxmax−Bxmin)Xoff=[(Bxmax−Bxmin)/2−Bxmax]XcorrYoff=[(Bymax−Bymin)/2−Bymax]Ycorr

3. Re-calculate the values of the magnetic field measured as:Bx′=Bxcorr+Bx+Bxoff By′=Bycorr By+Byoff

After obtaining the calibrated data, an object can be detected in any ofthe four possible quadrants, with respect to the co-ordinate centre(centre of the vehicle). FIG. 3 shows the curves 13, 14, 15 and 16representing the case where an object is present in each of thequadrants. The vertical axis shows the following calibrated values:Bxdif=Bx(r 1)−Bx(r 2)Bydif=By(r 1)−By(r 2)and the horizontal axis shows the angle turned (in sexagesimal degrees).

The calibrated values that are obtained when no object is present form astraight line c having the constant value e that is equivalent to 0.

Moreover, it is advisable to also obtain the data of the sum of thesignals from sensors r1 and r2 Bxsum and Bysum, as calibrated values,which are shown in FIG. 3 as well.

The Bydif data can be used to determine the quadrant containing theobject. By means of this data, and by knowing the orientation of thevehicle carrying the detection device in respect to the earth's magneticfield, it is possible to determine the quadrant containing the objectand, therefore, whether said object is in the blind spot. Therefore, forexample, curves 13 and 14 correspond to an object located in the frontof the sensor.

By means of this data and graphs equivalent to those in FIG. 1 (when thevehicle carrying the detection device is being overtaken by anothervehicle) and with the Bxsum, Bysum, Bxdif and Bydif values mentionedabove, it is possible to determine both the position of the object andits relative speed in relation to the sensor.

Generally, the signal detected by the sensor is amplified anddigitalised by means of the corresponding electronic circuit. The signalis very sensitive to all kinds of electromagnetic noise, particularlythe noise produced by the vehicle itself, for example by the indicators.Therefore, it is advisable to analyse and conveniently prepare the areaaround the desired location of the sensor, and to try and shield thesensor from possible sources of noise. It is also advisable to add anyfilters that may be required so as to obtain a signal that is asnoise-free as possible.

It is possible to perform the correction of the sensor data, in order tocompensate the distortion caused by the vehicle carrying the detectiondevice (the afore-mentioned calibration), on either the analogue ordigital signal.

In order to ascertain the vehicle's orientation with respect to theearth's magnetic field, information is collected on the three spatialcomponents in the detected magnetic field, and they are filtered andaveraged over time. The information on the possible presence of anobject is therefore determined once the vehicle is orientated and thesignals are received, as mentioned earlier. Moreover, it is possiblethat the detection device only works with magnetic field values havingjust two spatial components.

In some simple cases, the signal may be treated analytically since thereceived signals are sufficiently simple and void of superimposedeffects. However, in the case of more complex traffic situations, thereceived signals include a plurality of superimposed effects (othervehicles travelling in different directions or which are stopped,stationary elements on the roadside, etc). In these cases, it isadvisable to use a neural processor. This neural processor is able torecognise situations in which the vehicle carrying the detection deviceis being overtaken by an object (another vehicle) once it has completeda training stage. This means the analytical resolution of complexmathematical equations is unnecessary. The processor consists of aspecialised neuronal machine, designed in VLSI technology and capable ofimplementing a layer of a special type of artificial neural net: themultilayer perceptron. The recognition processor comprises a centralsequential process unit, connected to a parallel processor that is madeup of a series of process units or artificial neurons which operatesimultaneously on the same data and which are optimised for calculatingthe output from a neural net of a multilayer perceptron. The centralprocessor and the parallel processor are housed in a highly complexintegrated circuit based on semiconductors (chip). The neural net can betrained using various methods, such as for example the reactive tabusearch, or backpropagation, which are known to the person skilled in theart. The training is carried out by means of a selected database whichincludes relevant important and paradigmatic cases.

Logically, different kinds of neural nets can be used other than themultilayer perceptron which can be implemented as an executable programin a central sequential process unit.

1. A device for detecting the presence of objects in a blind spot of avehicle, said objects containing at least a ferromagnetic material orbeing manufactured by at least one ferromagnetic material whereby theydistort the earth's magnetic field, said device being of the type thatis mounted on the vehicle, said vehicle having at least one blind spot,where said detection device can detect said object located in said blindspot, characterised in that it is provided with means for detecting saiddistortion of said earth's magnetic field caused by said object.
 2. Thedetection device according to claim 1, characterised in that itcomprises: [1] at least one magnetic field sensor, capable of producingelectric signals in function of said magnetic field, [b] an electroniccircuit which converts said electric signals into digitalised signals,[c] a logical circuit that analyses said digitalised signals in order toanalyse the presence of said object in said blind spot, and whichproduces output signals that vary in function of the result of saidanalysis, and [d] indicator elements activated by said output signals.3. The detection device according to claim 2, characterised in that saidsensors are of the group made up of flux gate magnetometers (flux-gatesensor), Hall type sensors, magnetoinductive sensors andmagnetoresistive sensors.
 4. The detection device according to claim 2,characterised in that said sensors can detect at least two of the threespatial components in a magnetic field.
 5. The detection deviceaccording to claim 1, characterised in that it comprises a device formeasuring the inclination angle of said vehicle with respect to ahorizontal plane.
 6. The detection device according to claim 2,characterised in that said sensors have a resolution level less than orequivalent to 0.01 Gauss.
 7. The detection device according claim 2,characterised in that said sensors are current fed.
 8. The detectiondevice according to claim 1, characterised in that it reads saidmagnetic field at least once every 100 ms.
 9. The detection deviceaccording to claim 1, characterised in that it can distinguish whethersaid object is another vehicle approaching or another object.
 10. Thedetection device according to claim 2, characterised in that saidlogical circuit comprises neural nets.
 11. The detection deviceaccording to claim 2, characterised in that it has an action radius ofat least 4 meters, measured from each of said sensors.
 12. The detectiondevice according to claim 1, characterised in that it is provided with asensor housed within the outside rear view mirror assembly on saidvehicle.
 13. The detection device according to claim 12, characterisedin that it is provided with a sensor in each of the outside rear viewmirrors on said vehicle.
 14. The detection device according to claim 1,characterised in that it is provided with at least one sensor in therear of said vehicle.
 15. The detection device according to claim 1,characterised in that it is provided with two sensors positioned insymmetrical arrangement with respect to the longitudinal axis of thevehicle, and in that it calculates the difference between the signalsproduced by each of said sensors.
 16. The detection device according toclaim 2, characterised in that it is provided with calibrated datawhereby it is possible to subtract from the signal produced by each ofsaid sensors the part corresponding to the distortion of the earth'smagnetic field caused by the vehicle itself.
 17. The detection deviceaccording to claim 16, characterised in that it detects, in additionwhether said vehicle has begun to indicate that an object isapproaching.
 18. The detection device according to claim 17,characterised in that said activated indicator elements includes atleast one of the activated indicator elements from the group:illuminating the indicator light, turning the steering wheel, andactivating the door opening device.
 19. The detection device accordingto claim 18, characterised in that said indicator light include lightsignals having at least two colours, with each colour indicating adifferent warning level.
 20. The detection device according to claim 19,characterised in that said indicator light include an output elementwhich provides a pictogram representation, where said output element isa LED matrix or a screen.
 21. The detection device according to claim 1,where said vehicle is provided with doors equipped with a safety lock,characterised in that said device can act upon said lock.
 22. Thedetection device according to claim 1, characterised in that it includesother means for detecting the presence of objects, in addition to saidmeans for detecting said distortion of said earth's magnetic field.